DE2514930A1 - METHOD FOR OPTICAL DETERMINATION AND COMPARISON OF SHAPES AND LOCATIONS OF OBJECTS - Google Patents

Description

HUBERT BARON OF WELSE « LAWYER

ZUOELAaSEN AT THE LANDQERIOHTEN MÜNCHEN I UNO It ₁

AM OBERLANDESQERIOHT MÜNOHEN AND AM

BAYERiSOHKN OBERSTEN LANDESQERiOHT

MÜNOHEN 4O OANZIQER 8TRA88E IB TRMiPON oeo / a ei so so

March 26, 1975

25H930

Description of the invention

Process for the optical determination and comparison of shapes and positions of objects

Applicant;

Company OPTO Produkte AG Walchestrasse 19 CH-8006 Zurich / Switzerland

The invention relates to a method for the optical determination of deviations in shape / changes in shape and changes in position / at which generates patterns on the object by means of light beams and these are imaged by a photoelectronic device will.

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25U93Q

Determining the form deviation is a comparison of the actual form of an object to understand its nominal shape, which is achieved by a master object, a model after scale transformation or is represented by an ideal object that is only determined by calculation or drawing.

By determining the change in shape and the change in position, a comparison of the shape or position is a and to understand the same object in its temporal changes.

In addition to the form deviation, there is a positional deviation of an object compared to its master object, model, Calculated value or drawing defined target state possible, or a mere positional deviation without change of shape, e.g. if a turbine blade to be measured is at its angle to the axis of rotation of the turbine is twisted. The positional deviation, however, is only one aspect of the process technology discussed here Sub-case of the form deviation.

Determining and comparing the shape and position of objects as precisely as possible has a high level of accuracy in technology Has become important and important application examples are given below:

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When manufacturing complicated technical shapes, such as turbine blades or blades of ship propellers, the deviation from the target state, both both form and position can be determined in a form fidelity test. Vibrations of components can lead to their breakage, especially in the vicinity of the resonance range. You can by sound radiation cause serious environmental disturbances or the inoperability of entire systems, such as printing machines. To such To master vibrations, knowledge of their shape and amplitude is necessary. In a vibration analysis You can obtain the necessary information by comparing, for example, two positions of the vibrating component can be obtained. The deformation of components under static load can destroy them to lead. It is therefore necessary to avoid local peak loads during the construction. The possibilities computational solutions are often limited. It is possible, however, to attempt the places at maximum To determine the load by comparing the shape of the loaded state with the unloaded state. Due to material defects, E.g. casting defects in metals or delamination of car tires can cause irregular deformations occur under a given load, which is determined by the shape comparison of the state of the object before and at Change e.g. in the ambient pressure or the heat condition of the object or its static load can be determined in a material test.

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Probably the most common known method of dimensional accuracy comparison is the touching scanning of the test piece along a coordinate, whereby reference points are to be determined. This gives the contour in absolute values by displaying a clock or digitally and the actual value obtained in this way can be compared with the values of a masterpiece or with arithmetic values. However, the time and personnel expenditure is considerable. Laser technology enables a number of non-contact methods of dimensional accuracy comparison. In one of these processes, the laser beam is focused on a point on the surface and the transit time of the reflected beam is measured electronically according to the radar principle. This method is used, for example, for measuring tire molds. Holographic processes have not yet found their way into practice because of their complicated handling. They can only lead to digital results with considerable computational effort with the help of displacement vectors (compare Steinbichler et al.: "Quantitative evaluation of holograms" in Laser + Elektro-Optik No. 5/1973). In the grating projection method, which is not yet part of the published prior art, these disadvantages are largely avoided. An automatic evaluation is possible here, but requires a lot of effort (DP registration 24 10 947.5). Finally be on a

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Non-laser-technical method according to Takasaki pointed out, which admittedly from the effort and the handling is simple, but its measurement accuracy cannot be satisfactory (Takasaki: Moire Topography "In Applied Optics" 1970 pages 1467 to 72).

To analyze vibrations, so-called accelerometers are used to measure vibrations. which can be attached point by point. Sound emissions are measured with suitable microphones. The determination of fields presupposes a steady state. The holographic timeaver age method and double-pulse holography for aperiodic oscillations brought considerable results Progress. However, the restrictions made for holographic methods also apply here.

Numerous measurement methods are available for static construction optimization. These are enough from the point-by-point determination of the deformation with the help of probes to the measuring strips to the Tension optics. In this context, holographic interferometry offers considerable advantages. Compared to the tension optics, there are measurement options on the real object, compared to the strain gauge method the advantage of image capture. However, apart from the effort, the disadvantage is the excessive sensitivity of the holographic arrangement. The holographic evaluation is also problematic Interferograms, since the total deformation vector contributes to the interference indication, in general

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but only vector components are of interest. Above all, however, the digital representation is great Trouble.

In the case of non-destructive material testing, there were initially procedures with the use of ultrasound / X-rays, thermography, and acoustic emission are available through holographic methods were added. Their high sensitivity has the advantage that the error display is necessary Deformation is far from destruction. But it also has the disadvantage that with great effort the influence of boundary conditions, such as floor vibrations, must be eliminated.

Holographic interferometry is currently the most advanced technique on the in Area in question. The advantage of the pictorial information that can be achieved with it and the very high level of information Accuracy of the measurement has the disadvantage of large equipment expenditure and the not easy handling of the device as well as the need to adjust and avoid room influences. These Disadvantages complicate or prevent the direct use of these processes in industrial Production.

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The problem posed for the invention was therefore the development of a simple means devices that are not susceptible to failure and that can be used directly in industrial production Method with which while maintaining the measurement accuracy comparable to holographic methods Deviations in shape, changes in shape and changes in position are determined optically and in digital values can be implemented.

According to the invention, this object is achieved in that proceeding from a coherent light source Light rays through lenses or mirrors or holographically as a line or lines and / or arrangements of points are projected onto an object, and that this line, lines or arrangements of points imaged by means of an objective on an optoelectronic recording device and there in electrical impulses are converted, and that these impulses after an analog-digital conversion stored in an electronic arithmetic unit and digitally assigned to spatial coordinates will,

and that the values thus obtained correspond to the values obtained in the same way for the same object before his change of shape or position or with those of another ideal or real, his Target shape determining object are compared.

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A laser is expediently used as the source for the light rays used. Because of Due to its spatially coherent properties, the laser beam can reach very sharply defined points or Lines are focused. Although this focus or mapping applies strictly to only one level, achieved because of the small aperture of the beam, the relatively large depth of field / that for the measurement curved surfaces is necessary. The points or lines can be either lens or mirror optics as well as holographically. A single point or a single line becomes one of simplicity half with a lens or mirror optics. Will be multiple points or lines or curved Lines required for the measurement at the same time / so a holographic projection is particularly suitable. The holographic process also has the advantage that it is easy to replace the hologram enables rapid adaptation to changing conditions on the object or on the objects is. By changing the angle of the reference beam to the image plane of the hologram, a achieve such adjustment. Since holograms can be produced with very high efficiencies, the Loss of light with this method is negligible.

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Lines or points can be created by rotating the projection device or by other measures, e.g. by deflecting the beam, drive through entire areas of the object. Due to this temporal resolution, which, however, presupposes stationary conditions, large Areas on the object are measured. The stationary conditions can be checked by that on non-deforming surface areas of one and the same object or of different ones comparative objects on corresponding surface areas that are not subject to a form deviation simultaneously with the projected lines at least three reference points are projected, their position is stored in the arithmetic unit and from this with their changed position in one and the same object or with the position of the corresponding points are compared to the comparison object after performing a coordinate transformation through which the Changes in the position of the object and the object to be compared in relation to the object are suppressed to only to determine the pure change in shape or just the pure form deviation.

The mapping of the lines and point arrangements projected onto the object on the receiving surface of the optoelectronic arrangement can be done with the mapping of the Lines or arrangements of points according to shape deviation, change in shape or change in position of the object or objects

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in the arithmetic unit are brought to coincide as closely as possible by means of a coordinate transformation. As a result, changes in position can also be suppressed or in favor of examining the change in shape but conversely, neglecting the change in shape, the change in position or deviation can be determined. On the other hand, the projected reference points can be used to adjust the object, by the projected points with marks of the object or certain shape features of this object, e.g. corners, to be brought into cover.

The comparison object that determines the target shape when determining shape deviations is by no means necessary to be a real object of the same scale. The target form can be entered as digital values in the arithmetic unit can be entered. The line, the lines or the arrangements of points can also be enlarged or reduced nominal shape of the object representing the model and which is in the optoelectronic arrangement resulting values of the mapping of the lines or point arrangements in the Arithmetic unit can be converted into the values of the target shape of the object in a scale transformation.

The method described can be used for measuring the absolute shape of an object, for checking the accuracy of shape and for changing shape and position, both static and dynamic, for example as a vibration measurement. A sub-case of the change of position is

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the measurement of the level of liquids, at which the position or displacement of the surface the liquid is determined. The inventive method can also be used to measure the Speed of a moving object can be used, its change in position within a specific time or the duration of a specific change in position can be determined.

If larger areas are to be measured, several e.g. parallel lines can be used instead of a single line Lines projected simultaneously or with one Line the entire area can be tapped by pivoting the projection device. Let too In the case of larger objects, there is more than one projection arrangement with recording arrangements assigned to them in each case use, which in turn is assigned an arithmetic unit, whereby the projection and recording arrangement have a fixed spatial arrangement with one another Must have assignment that must be entered into the arithmetic unit as reference values.

The photo-electronic recording device can be a television camera or a single one Yes-no-statement delivering photodiode, if only the Location of a specific projected point

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should be determined, as this can be the case with vibration analyzes. With the individual Photodiode, the image can also be scanned step by step and line by line. For illustration more expansive Line or point patterns can be a photodiode array or a photodiode matrix or a Schottky detector Find use. In order to obtain digital values from a television camera, scanning can be used Electron beam counted clocks in the arithmetic unit are superimposed over a clock generator.

Embodiments of the invention are described in more detail below and in the drawings shown. Show it

Fig. 1

to 3 different representations of the beam path in a projection arrangement according to the invention with lenses and mirrors.

Fig. 4

and 5 different representations of the beam path in a holographic one according to the invention Projection arrangement.

6 shows a schematic representation of a device arrangement for carrying out the invention Procedure.

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As shown in FIG. 6, a line is drawn onto the object 2 by the projection arrangement 1 projected, which is a turbine blade that is examined for shape fidelity. The projection arrangement is housed in a box-shaped container in which a laser is provided as a light source is. The rays emanating from it 3 (Fig. 1 to 3) are, if a point-shaped Projection is desired, as shown in Fig. 1 through the lens 4 onto a pinhole 5 with very narrow opening focused. With the objective 6, this focus is imaged on the object in FIG. 7 as a point. If a projection in the form of a line is desired, a cylindrical lens is used after the objective 6 8 switched on, through which the projected Point is pulled apart to a line which is projected onto the object in FIG. Instead of As FIG. 3 shows, cylinder lens 8 can be a cylinder mirror 10 in the beam path after the beams have passed through be arranged by the divider cube 11. The rays projecting a line reflected from it are deflected laterally by the dividing cube 11.

Should more complicated patterns be projected, as is usually necessary, e.g. a line and three points, the holographic projection as shown in Figs. 4 and 5 is preferable. In points or lines are stored in the hologram 12.

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The points or lines are created by illuminating the hologram 12 with a reference beam 13 by diffraction. It can then be their real image, as shown in FIG. 4, or with the interposition of the objective 14, the virtual image of which is projected onto the object, as shown in FIG. 5.

The small aperture in the arrangements according to FIGS. 1 to 3 and in the holographic process a sufficient depth of field to over the entire curvature of the surface of the object 2 a very to obtain sharp, most accurate measurements permitting mapping of the points and lines.

The receiving arrangement 15, which in turn is housed in a box-shaped container, has an objective 16 that is projected onto the object Patterns of lines and points on a photoelectronic recording surface depicting the one TV camera or a photodxode matrix can be. In the former case runs with every line of the television picture a clock generator that delivers a thousand clocks per line. At the same time registered in the arithmetic unit 18 a counter the clocks. The location signal χ then takes place after a certain number of clocks at the intersection the line with the image of the projected Point or the projected line. Until then

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counted number of cycles is the searched digital value.

In the case of a photodiode array, each line is traversed with a stepper motor. The location signal χ then arises from the mentioned photodiode and is therefore already present as a digital value as well like the digital value of the respective line.

The digital values obtained are fed to the arithmetic unit 18, the measured values χ as Function of y and ζ can be entered into memory 19. When using only one photodiode, e.g. with level measurement, only a value of χ is obtained, which can then appear in a digital display. In the event of a form deviation, deformation or change in position first the values of the master object or the original condition of the object stored, these values also being stored directly, for example as computationally determined values can be entered via the memory 19. On the test object or after deformation or change of position on The test object, the values for x, y and ζ are determined in the same way and transferred to the memory 19. The stored values then flow to the computer 20, which makes the comparison between the actual and desired state or between the original and the test state by forming the difference. These

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represents the measure of the form deviation or the position difference, which is expressed in units of length, e.g. is converted into millimeters. The influence of the relative movement can be influenced by a coordinate transformation must be taken into account between the object and the measuring system.

The data output 21 can finally be a curve recorder (x, y recorder), a printer or a Be digital display with light-emitting diode digits. For control purposes, a monitor can be used with the mounting arrangement be connected.

about relative movements between the object 2 on the one hand and turn off the projection arrangement 1 and the receiving arrangement 15 on the other hand

or

Projection arrangement and / the recording arrangement be firmly arranged on the object.

Claims

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Claims (16)

Claims Process for the optical determination of form deviations, Changes in shape and position, in which patterns of light are generated on the object and these be mapped by an optoelectronic device, characterized in that light rays (3) emanating from a coherent light source are projected onto an object through lenses (4,6,8) or mirrors (10,11) or holographically as line or lines and / or point arrangements, and that this line, lines or arrangements of points by means of an objective (16) on an optoelectronic Recording device mapped and converted into electrical impulses there, and that these pulses are stored in an electronic arithmetic unit (18) after an analog-digital conversion and spatial coordinates are assigned digitally, and that the resulting values are identical to those in Wise obtained values of the same object before its shape or position change or with those of one other ideal or real objects that determine its desired shape will be compared. 2. The method according to claim 1, characterized in that the light rays (3) by diffraction in a hologram (12) as a line or lines 609842/0486 25Η930 or point arrangements with adaptation to the shape of the object (2) on this as a virtual or real image can be projected. 3. The method according to claim 1, characterized / that the adaptation to the shape of the object (3) is carried out by changing the angle of the reference beam (13) to the image plane of the hologram (12). 4. The method according to claim 1, 2, 3, characterized in that on non-deforming surface areas of one and the same object (2) or on surface areas with known deformation de or for different objects to be compared / objects (2) not subject to a form deviation corresponding surface areas or on surface areas with known shape deviation at the same time at least three reference points with the projected lines are projected, their position in the arithmetic unit (18) and stored by this with their changed position with one and the same object or with the position of the corresponding points on the object to be compared after carrying out a coordinate transformation be compared, by the changes in position of the object or the comparison object in relation to the object are suppressed in order to allow only the pure change in shape or only the pure form deviation determine. 609842 / CU86 4 $ 25U930 5. The method according to claim 1, 2, 3/4, characterized in that the mapping of the projected onto the object lines and point arrangements on the receiving surface of the optoelectronic arrangement with the mapping of the lines and / or point arrangements after shape deviation, change in shape or change in position of the object or objects in the arithmetic unit (18) by a coordinate transformation in the greatest approximation is brought to congruence. 6. The method according to claim 1, 2, 3, 4, 5, characterized in that the object (2) is adjusted by means of the point arrangement projected onto it. 7. The method according to claim 1, 2, 3, 4, 5, 6, characterized in that the nominal shape of the ideal object is entered as digital values in the arithmetic unit (18). 8. The method according to claim 1, 2, 3, 4, 5, 6, characterized in that the line, the lines or the point arrangements are projected onto a model representing the enlarged or reduced nominal shape of the object (2) and the values of the mapping of the lines or point arrangements in the arithmetic unit (18) resulting in the optoelectronic arrangement in a scale transformation can be converted into the values of the nominal shape of the object (2). 609842/0486 ¹⁰ 25Η930 9. The method according to claim 1,2,3 / 4,5,6,7,8, characterized in that it is used to measure the absolute shape of an object. 10. The method according to claim 1, 2, 3, 4, 5, 6, 7, 8, characterized in that it is used to measure the dimensional accuracy of an object. 11. The method according to claim 1,2,3,4,5,6,7,8, characterized in that it is used for static and dynamic deformation measurements. 12. The method according to claim 1, 2, 3, 4, 5, 6, 7, 8, characterized in that it is used to measure the level of liquids. 13. The method according to claim 1,2,3,4,5,6,7,8, characterized in that it is used to measure the speed of a moving object. 14. Measuring arrangement for carrying out the method according to claim 1,2,3,4,5,6,7,8,9,10,11,12,13, characterized in that a projection arrangement (1) is provided which serves as the light source has a laser, in whose beam path (3) lenses (4, 6, 8), mirrors (10, 11) and / or a hologram (12) are provided, which the rays emanating from the laser as a line or lines or an arrangement of points project onto an object (2), 609842/0486 also that an optical recording arrangement (15) is provided in which the line, lines or the arrangement of points on a photoelectronic surface are mapped and in which this mapping can be converted into electrical impulses, and that Finally, an electronic arithmetic and logic unit (18) is provided which converts these pulses into an analog-to-digital process store and use the digital values obtained in the same way in the form of the in can compare its position or shape changed object or with the shape of another object. 15. Measuring arrangement according to claim 14, characterized in that more than one projection arrangement (1) with recording arrangements (15) assigned to this projection arrangement is provided, as well as an arithmetic unit (18) assigned to this recording device for recording the electrical impulses converted in the recording device, these projection and recording arrangements (1 , 15) have a fixed spatial allocation to one another, which is entered as a reference value in the computing device. 16. Measuring device according to claim 9, characterized in that it is attached to the object (2) itself. 609842/0486 Blank page